1. Field of the invention
This invention relates to improvements of the outer faces of piston shoes of radial piston pumps, motors, transmissions, compressors and engines. Such outer faces slide along the inner face of a piston stroke actuator or guide ring. The outer faces of the piston shoes of the invention and of the field in the art, commonly have hydrostatic bearings to carry a radial load. The present invention deals with the improvement of those portions of the outer faces of piston shoes which supply in addition to the hydrostatic bearing capacity and in addition to probable smaller hydrodynamic bearing capacities an improved hyrodynamic bearing capacity.
2. Description of the prior art
The application of hydrostatic bearings in the outer faces of piston shoes which are also called slide faces of piston shoes has obtained a high perfection, as is for example known from my U.S. Pat. No. 4,212,230.
Hydrodynamic bearing portions are also already known, for example, from my U.S. Pat. No. 4,037,523. Related to the art are also U.S. Pat. Nos. 4,018,137, 4,258,548, French Pat. No. 197,810 or others. The mentioned French patent deals with axial pistons and can carry a load hydrodynamically only around a point. The obtained bearing capacity is therefore, almost neglectible, small. U.S. Pat. No. 4,018,137 has a slide face which is parallel to the guide face of the piston stroke guide. Parallel faces can not create effective hydrodynamic bearing capacity. This patent thereby errs when it assumes that the piston shoe would carry a considerable radial load by hydrodynamic bearing action. U.S. Pat. No. 4,258,548 provides or attempts to provide hydrodynamic bearing portions but fails to separate them from the hydrostatic bearing portion. The effects and results of the actions are, thereby, not exactly known. They interfere with each other. A maximal result of bearing capacity can not be obtained. My U.S. Pat. No. 4,037,523 and the other mentioned patents, as well as other patents in the art, fail to give teachings how to obtain the desired effects. They can, therefore, also not obtain the desired effective results. The defects of the former art shall be overcome or become reduced by the present invention.